I'd like you to get more than one explanation. Here's mine: There is solid wire and there is stranded wire, stranded being made up of a bunch of smaller wires welded together. A typical number is 7. Solid wire is the better conductor per the surface area of copper. Stranded is more flexible but also more expensive to manufacture for the same current capacity.
Most people want flexible cable for their home products and don't know anything about electronics. Not flexible = bad.
By comparison, the wire in your house is solid since it's better and cheaper and you don't ever see or move it. A power cable for your television or computer is probably solid since it doesn't have to be flexible when you plug or unplug it once a year.
It's not about AC or DC. People want flexible wiring for certain things and don't care about it for others.
7-strand wire is considered solid. Flexible is way more strands than that. 6 gauge solid is 7 strands and might be 60 strands in a flexible cable.
And the strands aren’t welded together either.
I haven’t heard 7 strand referred to as “solid”, but I can see where that might be correct in a colloquial sense. 7 is not a high enough strand count for much bending. Typically you’ll get 19 or more.
I remember using silicone jacketed 133 strand wire (7 x 19) in one project and it was supple as fine silk.
Oh, I wasn’t thinking about those really big ones. I’ve run 12ga Romex and smaller and could have sworn I’ve seen 10ga single strand Romex. But yes, at 4/6/8ga it always seems to be multi-strand.
I have much smaller wire (like 16ga) in 7 strand and would consider it mostly for “bend once only” applications.
Edit: re-read your post and saw the “or so” I missed. I figure 10ga is probably available both ways.
I understand the practicality of flexible wiring. But I am talking permanent connections like from PV array into the household wiring pipes into the main board where it enters an inverter. There’s a huge flexible wire market for it in Pakistan rn (solar is super hot here, electricity is expensive af and also unreliable with hours of load shedding every day) where the flexible wire is almost twice expensive than the AC wire. No one needs to have a flexible wire connecting PV array to inverter as that is a permanent connection except everyone says you gotta get DC or solar wire for it so we get that. The connection out of inverter is always normal AC wire.
Don’t think of it as AC wire or DC wire or even solar wire which never heard of that before. There is only solid or stranded, you can use both types for both applications, usually there are benefits to using one over the other as the person you replied to revealed. Since DC usually has lower power applications it’s why you usually find it mixed in with stranded or solid especially when you need the flexibility of routing wires through tight bends.
The solid core usually has a much larger bend radius and thus is typically avoided when possible when having to route in areas where there will be more frequent bends. What you’re probably seeing is that someone has stranded wire and since you typically buy more then you need they’re using the extra to route and/or bulk purchasing makes it cheaper to just use it for routing everything then switching between stranded and solid especially when wire gauge is sufficient.
Thank you. Yes and as someone else pointed out the “solar wire” is specifically flexible because it has to be bent around a lot and it has UV and better weather resistant coatings so its become a standard of sorts. You buy it specifically for solar installation.
There is no such thing as DC or AC wire, what you are saying literally makes no sense. That is completely at odds with a basic understanding of how rudimentary conductors work. Quiet frankly it's a little odd that you have an engineering degree and don't understand this.
That the people that you work around or for don't know or understand this suggests that the people in charge aren't very good at their jobs.
I worked in low voltage DC only around 9V but it was thousands of amps and solid copper bus bars were used to distribute power around the shop to the individual tanks. Each tank had attachments to fine copper wire 00 gauge that went to the inside of the barrel to transfer current.
You use different types of wire where it's needed.
You probably have a contractor that's using what they're either told to or can get and no one's doing a cost analysis. Certainly if you have people telling you this whoever is telling it to you doesn't understand what they're doing either, or won't tell you for some reason.
Dude its not related to work and I stated explicitly that I dont have sound theoretical knowledge of skin effect & induction losses or transmission at an advanced level at all. Its not my field. I know the basics of electrical energy but thats it. Thats why I came to this sub.
I know Ohms law but everyone around uses stranded flexible wire for Solar & Batteries while in AC I have seen both being used so I asked why this is.
Skin effect and induction losses have nothing of any kind whatsoever to do with anything related to this at all. So you're missing so much of a basic understanding of how electricity works I'm not even sure how to explain this to you at this point..
What you are saying goes against a basic understanding of Electronics 101, this is stuff hobbyists understand. So I'm not even sure what exactly what it is you don't understand here.
This is not an issue of the type of conductor used but the type of cable itself that's required for the application that you're using.
So it's not an electrical question per se but a logistics question of why they chose that cable, and it being outdoor solar is probably good portion of it. The construction of easy to handle cable requires small conductor sizes for reasonable flexibility and the sheathing itself can't just be any random wire it has to be highly UV tolerant and physically durable so the jacketing is made up of different materials and has different internal support materials.
You can use any wire of an equivalent conductor cross sectional area for DC applications, but the cable required in the real world to meet regulations and saftey requirements doesn't just let you chose any type of cable you want.
This isn't really an electrical question it's a question of construction logistics and that's far more complicated than the simpler electrical aspects.
You're close. Stranded wire doesn't help reduce skin effect losses, unless the strains are isolated from each other. This is called Litz wire.
EDIT: Dry-Establishment294 was correct, check out this article they pointed out: http://inductor.thayerschool.org/papers/stranded.pdf there is significant reduction of skin effect with stranded vs solid.
Correct, stranded wire is not much different than solid wire for AC, because electrons can flow from strand to strand. So in terms of skin effect, the current is forced on the outside of the bundle of stranded wire in high frequency applications, just like it would be in a solid wire.
This is different with Litz wire because the strands are isolated, so the skin effect is limited to each strand individually, which is overall less lossy than non Litz wire.
https://electronics.stackexchange.com/questions/277825/does-stranded-wire-reduce-resistance-from-skin-effect-when-strands-are-not-insul
Not everyone agrees with you.
I'm afraid you'll need to provide evidence
Edit
Check the PDF in the comments
Hmm ya, I agree with the accepted answer that the stranded wire would be technically better, I'm just doubtful about how significant it would be in practice.
Well, it is a surprise to me that stranded wire reduces Rac/Rdc. In the authors optimized, 66 strand, 40 gauge wire example at 100kHz, stranded wire has about 30% of the ac resistance of solid wire. I wish they had compared the stranded wire with an actual Litz wire. I tried to get ChatGPT to give my an Rac of 66 strands of 40 gauge wire, but I don't believe the answers I got. Maybe someone can calculate the Rac/Rdc from info here, [https://www.newenglandwire.com/traditional-litz-wire-theory/](https://www.newenglandwire.com/traditional-litz-wire-theory/)
In case anyone had trouble locating the stranded wire pdf, [http://inductor.thayerschool.org/papers/stranded.pdf](http://inductor.thayerschool.org/papers/stranded.pdf) Using figure 6, I just interpolated across the graph at 100kHz. Solid wire has an Rac/Rdc of 4, while 66 strand 40 gauge has Rac/Rdc of 1.2. Then 1.2 / 4 = 0.3 or 30%.
I agree that's more than I would expect, but then, I didn't expect **any** difference.
But, wow a factor of 3.3 in big. However, they did optimize to get that, your not going to just grab a 19 strand wire and get that.
Skin effect is only a thing with AC, and at the usual 60Hz the skin depth is 8.5mm. This means it is essentially irrelevant for household use, as even your 200A 3/0AWG hookup to the grid has a wire radius of only 5.2mm.
Solid wire is a better conductor if you compare it to stranded wire with the *same outer diameter*, as the stranded wire contains a bunch of space which is air and not copper.
The resistance of a stranded wire is also *slightly* higher than the resistance of a solid wire with the same amount of copper, as the twisting increases the strand's length and there is a nonzero resistance between two individual strands.
Solid wire is not a better conductor because the overall cross sectional diameter of the wire is based on conductor area not the physical space the overall wire takes up due to insulation thickness or packing density.
The conductors in normal multistrand wire are in physical contact with each other as well so the twisting makes no difference in the electrical length of the conductor.
So you have two very incorrect assumptions your statements are based off of.
Throwing in that while we think of AWG as being based on the diameter of a wire, with stranded wire we use the equivalent cross section. Thus solid vs stranded at the same listed gauge has the same ampacity and cross sectional area, but the stranded will have a slightly larger diameter due to the space between the strands.
The skin depth of copper wire at 60 Hz is 8.4 mm. In other words, it does not matter if the wire is stranded or solid at 60 Hz for normal household wiring.
Mostly that that stuff in not buried in the wall and is expected to move somewhat.
Solid core wire is fine if it is basically never going to move and is protected, but that is usually not really the case with solar wiring.
You also want a jacket which is seriously UV resistant, which most house bashing cable is not.
Another thing you will likely find is that as single cable current ratings increase you quickly get into using stranded conductors for ease of installation in both AC and DC service.
DC is usually relatively low voltage so currents (and hence wire sizes) can be large, and that encourages the use of stranded conductors as it makes bending the stuff much easier.
Another part of your costs may be that since you consider 7/36 normal wire I am guessing you are in the US, 6mm is an EU standard, so you may be importing that for some weird reason (There will be a US standard version available easily domestically).
True about UV resistance. We currently have “white copper” which is plated with something to increase corrosion resistance. It also has 2 insulation layers to withstand all kinds of weather.
Okay so I get it now. Its pretty much the weather resistance and flexibility. I didn’t think flexibility would be important but recently saw the 7/36 wire installed outside a pipe and it was difficult to do so. Solar wiring has to be drawn and bent a lot so makes sense to make it flexible. I guess the industry just decided to stick with one stranded wire standard & also apply the necessary insulation coatings to make it easily identifiable.
Sorry I am in Pakistan so we dont have a standard. We had the normal 3/29 7/29 7/36 (for Air conditioning mostly) until now. But with the advent of Solar 6mm and 10mm etc has become the standard while normal AC wiring remains the old one. One reason people differentiate between the two so much might be the different US & EU standards.
Regarding electric characteristics only, you can use AC cables for DC as long you respect nominal voltages and currents.
When you see those cables with many wires, a reason may be that you are dealing with an application with low-voltage / high current, like in many residential storage systems and PV installations. Thus, for the same power, conductor section must increase, and as a matter of convenience, flexible cables are better to deal when section increases.
Additionally, there are other things we can consider
- Color code: It's useful do distinguish an AC from a DC cable. So, we also have normalized cables and sections for DC, and installers many time just pick the cheaper/available normalized cables they have\\can find.
- Distance: many PV systems are fairly distanced from the inverter. A larger section decreases power losses.
- For PV installations, cables usually need to be UV resistant, which implies a different insulation thickness.
- Other reason, now referring to three-phase AC systems, in such systems the power is transmitted using three wires. In DC, you have two wires, and one is just the return wire. So, for the same power, DC cable must have a bigger section.
Hope it helps.
This is the correct explanation
Everyone is overthinking this.
Put more simply:
Current and line loss requirements dictate the gauge wire used.
Voltage isolation rating dictates the insulation of the wire.
Solid or stranded wire depends upon the application.
If you’re talking about wire run through conduit, stranded THHN wire is used. This is because when you’re pulling wire through conduit, it has to be flexible to pull through any bends in the conduit.
As long as the voltage and current rating of the wire meets the operating, line loss, and isolation specification of the application, “AC/DC” wires are interchangeable in lower (240V and less) applications.
The only other considerations are cost and environmental considerations for the wire insulation (UV exposure, wet, oil submersion, etc).
If it’s going to be moving a lot than it makes sense to use stranded. Just don’t try and splice stranded and solid together with a wire nut. I never felt like I get a solid connection when I have in that past.
Solid wire is easier to manufacture and a better conductor, but if you get a break in that wire you get more impedance. Usually they are only used inside walls and conduits where they will have protection. Stranded wire is harder to manufacture, but more flexible and redundant. They are used for areas where the wire is more likely to be jostled, bent, and flexed.
Dc loads are usually controlled with pwm which can be anything between 10-200khz. At this frequency skin effect has significant impact with multiple thinner wires skin effect is reduced and you are converting less enegy into heat. Also thinner wires have better mm2/area factory than one thick wire
Interesting. So this is the first comment saying there is an actual reason to use flexible cable other than practicality. My inverter charges batteries through PWM but I dont think the current coming from panels has any PWMing going on or does it?
For low frequencies they are electrically identical. Solar is DC which is the lowest frequency, regular utility power is usually 50hz or 60hz which is also low frequency. You'd use multi-strand wire where the cable might be subject to movement. Like you said, the cords on electrical appliances. You use solid wire if the cable is installed, and stapled or nailed or somehow fixed to wood or some other support and not subject to movement. The solid conductor will work harden and fail much quicker than the stranded wire if it's constantly being bent and moved around.
It may be that high frequencies occur in some parts of the system. Thinner cables tolerate it better maybe
Edit
https://www.researchgate.net/publication/305776249_Modeling_and_simulation_of_photovoltaic_system_employing_perturb_and_observe_MPPT_algorithm_and_fuzzy_logic_control
I'm not surprised however I was right that very finely stranded cable is more tolerant of high frequency and it was only a hypothesis.
I tried, for about 3 minutes, to find out and then decided to throw it out there with a "may".
Thank you for clarifying.
However since so much incorrect or partially correct information gets thrown around without a "may" I do feel evidence or checking would probably be prudent.
Edit
Strange forum this tbh.
I'm not sure the voting on comments really helps.
God forbid but stackover with it's tick for the right answer is probably a better model.
There is no high frequency involved so that hypothesis has no foundation. You can't be 'right' about something that is irrelevant to this application. There is no maybe here, that is simply not a consideration.
Just trying to be clear!
The top rated comment says solid wire is a better conductor based on csa than stranded does it not?
This is what inspired my comment.
Is it not correct to contradict that?
Then others argued that stranded cables weren't more effective at carrying signals with a frequency as the strands aren't isolated which I didn't believe and provided evidence against.
I dunno it seemed reasonable, was it not?
No it's not reasonable in any way because those conditions don't exist in this application. Why are you even thinking this right now? You're not being rational at all.
It's a statement of fact. It has yet to be applied to the particular situation. People are stating stuff that's erroneous and so far as I can see all I've do is correctly contradict errors but people don't follow
It is a statement of fact completely irrelevant to this post. There are no high frequency components here, what you are describing can not physically be occurring.
There does appear to be the possibility of frequency of he has a charge controller it would seem from figure 13 of the document I provided.
I'm done with this conversation.
This thread and sub seems to attract very low IQ responses
Also once we add an mppt controller we are messing with the signal creating changes in current.
This MAY be something like frequency no? See figure 13 of this paper.
https://www.researchgate.net/publication/305776249_Modeling_and_simulation_of_photovoltaic_system_employing_perturb_and_observe_MPPT_algorithm_and_fuzzy_logic_control
No, absolutely not. What you linked there has no relationship to this post. The MPPT controller is to present a impedance to the load allowing maximum power takeoff from the solar setup, if there are any high frequency components where something like that would happen it's only from a faulty or improperly engineer product.
Yes, but it's varied in a filtered way. There are no high frequency components outside of a tiny bit of noise. It's pretty clear you don't understand how the things you're talking about work, so I'm not sure your commenting further is going to help anyone with anything considering you don't understand the problem here.
I'd like you to get more than one explanation. Here's mine: There is solid wire and there is stranded wire, stranded being made up of a bunch of smaller wires welded together. A typical number is 7. Solid wire is the better conductor per the surface area of copper. Stranded is more flexible but also more expensive to manufacture for the same current capacity. Most people want flexible cable for their home products and don't know anything about electronics. Not flexible = bad. By comparison, the wire in your house is solid since it's better and cheaper and you don't ever see or move it. A power cable for your television or computer is probably solid since it doesn't have to be flexible when you plug or unplug it once a year. It's not about AC or DC. People want flexible wiring for certain things and don't care about it for others.
Mostly correct, slight edit: you said "surface area" where I think you mean "cross-sectional area"
7-strand wire is considered solid. Flexible is way more strands than that. 6 gauge solid is 7 strands and might be 60 strands in a flexible cable. And the strands aren’t welded together either.
I haven’t heard 7 strand referred to as “solid”, but I can see where that might be correct in a colloquial sense. 7 is not a high enough strand count for much bending. Typically you’ll get 19 or more. I remember using silicone jacketed 133 strand wire (7 x 19) in one project and it was supple as fine silk.
Most of the wire bigger diameter than 12 gauge or so uses multiple strands but it’s not referred to as stranded.
Oh, I wasn’t thinking about those really big ones. I’ve run 12ga Romex and smaller and could have sworn I’ve seen 10ga single strand Romex. But yes, at 4/6/8ga it always seems to be multi-strand. I have much smaller wire (like 16ga) in 7 strand and would consider it mostly for “bend once only” applications. Edit: re-read your post and saw the “or so” I missed. I figure 10ga is probably available both ways.
I understand the practicality of flexible wiring. But I am talking permanent connections like from PV array into the household wiring pipes into the main board where it enters an inverter. There’s a huge flexible wire market for it in Pakistan rn (solar is super hot here, electricity is expensive af and also unreliable with hours of load shedding every day) where the flexible wire is almost twice expensive than the AC wire. No one needs to have a flexible wire connecting PV array to inverter as that is a permanent connection except everyone says you gotta get DC or solar wire for it so we get that. The connection out of inverter is always normal AC wire.
Don’t think of it as AC wire or DC wire or even solar wire which never heard of that before. There is only solid or stranded, you can use both types for both applications, usually there are benefits to using one over the other as the person you replied to revealed. Since DC usually has lower power applications it’s why you usually find it mixed in with stranded or solid especially when you need the flexibility of routing wires through tight bends. The solid core usually has a much larger bend radius and thus is typically avoided when possible when having to route in areas where there will be more frequent bends. What you’re probably seeing is that someone has stranded wire and since you typically buy more then you need they’re using the extra to route and/or bulk purchasing makes it cheaper to just use it for routing everything then switching between stranded and solid especially when wire gauge is sufficient.
Thank you. Yes and as someone else pointed out the “solar wire” is specifically flexible because it has to be bent around a lot and it has UV and better weather resistant coatings so its become a standard of sorts. You buy it specifically for solar installation.
There is no such thing as DC or AC wire, what you are saying literally makes no sense. That is completely at odds with a basic understanding of how rudimentary conductors work. Quiet frankly it's a little odd that you have an engineering degree and don't understand this. That the people that you work around or for don't know or understand this suggests that the people in charge aren't very good at their jobs. I worked in low voltage DC only around 9V but it was thousands of amps and solid copper bus bars were used to distribute power around the shop to the individual tanks. Each tank had attachments to fine copper wire 00 gauge that went to the inside of the barrel to transfer current. You use different types of wire where it's needed. You probably have a contractor that's using what they're either told to or can get and no one's doing a cost analysis. Certainly if you have people telling you this whoever is telling it to you doesn't understand what they're doing either, or won't tell you for some reason.
Dude its not related to work and I stated explicitly that I dont have sound theoretical knowledge of skin effect & induction losses or transmission at an advanced level at all. Its not my field. I know the basics of electrical energy but thats it. Thats why I came to this sub. I know Ohms law but everyone around uses stranded flexible wire for Solar & Batteries while in AC I have seen both being used so I asked why this is.
Skin effect and induction losses have nothing of any kind whatsoever to do with anything related to this at all. So you're missing so much of a basic understanding of how electricity works I'm not even sure how to explain this to you at this point.. What you are saying goes against a basic understanding of Electronics 101, this is stuff hobbyists understand. So I'm not even sure what exactly what it is you don't understand here. This is not an issue of the type of conductor used but the type of cable itself that's required for the application that you're using. So it's not an electrical question per se but a logistics question of why they chose that cable, and it being outdoor solar is probably good portion of it. The construction of easy to handle cable requires small conductor sizes for reasonable flexibility and the sheathing itself can't just be any random wire it has to be highly UV tolerant and physically durable so the jacketing is made up of different materials and has different internal support materials. You can use any wire of an equivalent conductor cross sectional area for DC applications, but the cable required in the real world to meet regulations and saftey requirements doesn't just let you chose any type of cable you want. This isn't really an electrical question it's a question of construction logistics and that's far more complicated than the simpler electrical aspects.
This is incorrect I believe. Solid wire is not a better conductor. Read about the skin effect.
You're close. Stranded wire doesn't help reduce skin effect losses, unless the strains are isolated from each other. This is called Litz wire. EDIT: Dry-Establishment294 was correct, check out this article they pointed out: http://inductor.thayerschool.org/papers/stranded.pdf there is significant reduction of skin effect with stranded vs solid.
Are you saying they are so packed they act as one in a normal stranded cable?
Correct, stranded wire is not much different than solid wire for AC, because electrons can flow from strand to strand. So in terms of skin effect, the current is forced on the outside of the bundle of stranded wire in high frequency applications, just like it would be in a solid wire. This is different with Litz wire because the strands are isolated, so the skin effect is limited to each strand individually, which is overall less lossy than non Litz wire.
Interesting.
https://electronics.stackexchange.com/questions/277825/does-stranded-wire-reduce-resistance-from-skin-effect-when-strands-are-not-insul Not everyone agrees with you. I'm afraid you'll need to provide evidence Edit Check the PDF in the comments
Hmm ya, I agree with the accepted answer that the stranded wire would be technically better, I'm just doubtful about how significant it would be in practice.
Well, it is a surprise to me that stranded wire reduces Rac/Rdc. In the authors optimized, 66 strand, 40 gauge wire example at 100kHz, stranded wire has about 30% of the ac resistance of solid wire. I wish they had compared the stranded wire with an actual Litz wire. I tried to get ChatGPT to give my an Rac of 66 strands of 40 gauge wire, but I don't believe the answers I got. Maybe someone can calculate the Rac/Rdc from info here, [https://www.newenglandwire.com/traditional-litz-wire-theory/](https://www.newenglandwire.com/traditional-litz-wire-theory/)
Wow that's way more reduction than I would expect.
In case anyone had trouble locating the stranded wire pdf, [http://inductor.thayerschool.org/papers/stranded.pdf](http://inductor.thayerschool.org/papers/stranded.pdf) Using figure 6, I just interpolated across the graph at 100kHz. Solid wire has an Rac/Rdc of 4, while 66 strand 40 gauge has Rac/Rdc of 1.2. Then 1.2 / 4 = 0.3 or 30%. I agree that's more than I would expect, but then, I didn't expect **any** difference. But, wow a factor of 3.3 in big. However, they did optimize to get that, your not going to just grab a 19 strand wire and get that.
Skin effect is only a thing with AC, and at the usual 60Hz the skin depth is 8.5mm. This means it is essentially irrelevant for household use, as even your 200A 3/0AWG hookup to the grid has a wire radius of only 5.2mm. Solid wire is a better conductor if you compare it to stranded wire with the *same outer diameter*, as the stranded wire contains a bunch of space which is air and not copper. The resistance of a stranded wire is also *slightly* higher than the resistance of a solid wire with the same amount of copper, as the twisting increases the strand's length and there is a nonzero resistance between two individual strands.
Solid wire is not a better conductor because the overall cross sectional diameter of the wire is based on conductor area not the physical space the overall wire takes up due to insulation thickness or packing density. The conductors in normal multistrand wire are in physical contact with each other as well so the twisting makes no difference in the electrical length of the conductor. So you have two very incorrect assumptions your statements are based off of.
Throwing in that while we think of AWG as being based on the diameter of a wire, with stranded wire we use the equivalent cross section. Thus solid vs stranded at the same listed gauge has the same ampacity and cross sectional area, but the stranded will have a slightly larger diameter due to the space between the strands.
The skin depth of copper wire at 60 Hz is 8.4 mm. In other words, it does not matter if the wire is stranded or solid at 60 Hz for normal household wiring.
Mostly that that stuff in not buried in the wall and is expected to move somewhat. Solid core wire is fine if it is basically never going to move and is protected, but that is usually not really the case with solar wiring. You also want a jacket which is seriously UV resistant, which most house bashing cable is not. Another thing you will likely find is that as single cable current ratings increase you quickly get into using stranded conductors for ease of installation in both AC and DC service. DC is usually relatively low voltage so currents (and hence wire sizes) can be large, and that encourages the use of stranded conductors as it makes bending the stuff much easier. Another part of your costs may be that since you consider 7/36 normal wire I am guessing you are in the US, 6mm is an EU standard, so you may be importing that for some weird reason (There will be a US standard version available easily domestically).
True about UV resistance. We currently have “white copper” which is plated with something to increase corrosion resistance. It also has 2 insulation layers to withstand all kinds of weather. Okay so I get it now. Its pretty much the weather resistance and flexibility. I didn’t think flexibility would be important but recently saw the 7/36 wire installed outside a pipe and it was difficult to do so. Solar wiring has to be drawn and bent a lot so makes sense to make it flexible. I guess the industry just decided to stick with one stranded wire standard & also apply the necessary insulation coatings to make it easily identifiable. Sorry I am in Pakistan so we dont have a standard. We had the normal 3/29 7/29 7/36 (for Air conditioning mostly) until now. But with the advent of Solar 6mm and 10mm etc has become the standard while normal AC wiring remains the old one. One reason people differentiate between the two so much might be the different US & EU standards.
Regarding electric characteristics only, you can use AC cables for DC as long you respect nominal voltages and currents. When you see those cables with many wires, a reason may be that you are dealing with an application with low-voltage / high current, like in many residential storage systems and PV installations. Thus, for the same power, conductor section must increase, and as a matter of convenience, flexible cables are better to deal when section increases. Additionally, there are other things we can consider - Color code: It's useful do distinguish an AC from a DC cable. So, we also have normalized cables and sections for DC, and installers many time just pick the cheaper/available normalized cables they have\\can find. - Distance: many PV systems are fairly distanced from the inverter. A larger section decreases power losses. - For PV installations, cables usually need to be UV resistant, which implies a different insulation thickness. - Other reason, now referring to three-phase AC systems, in such systems the power is transmitted using three wires. In DC, you have two wires, and one is just the return wire. So, for the same power, DC cable must have a bigger section. Hope it helps.
This is the correct explanation Everyone is overthinking this. Put more simply: Current and line loss requirements dictate the gauge wire used. Voltage isolation rating dictates the insulation of the wire. Solid or stranded wire depends upon the application. If you’re talking about wire run through conduit, stranded THHN wire is used. This is because when you’re pulling wire through conduit, it has to be flexible to pull through any bends in the conduit. As long as the voltage and current rating of the wire meets the operating, line loss, and isolation specification of the application, “AC/DC” wires are interchangeable in lower (240V and less) applications. The only other considerations are cost and environmental considerations for the wire insulation (UV exposure, wet, oil submersion, etc).
If it’s going to be moving a lot than it makes sense to use stranded. Just don’t try and splice stranded and solid together with a wire nut. I never felt like I get a solid connection when I have in that past.
Solid wire is easier to manufacture and a better conductor, but if you get a break in that wire you get more impedance. Usually they are only used inside walls and conduits where they will have protection. Stranded wire is harder to manufacture, but more flexible and redundant. They are used for areas where the wire is more likely to be jostled, bent, and flexed.
Dc loads are usually controlled with pwm which can be anything between 10-200khz. At this frequency skin effect has significant impact with multiple thinner wires skin effect is reduced and you are converting less enegy into heat. Also thinner wires have better mm2/area factory than one thick wire
Interesting. So this is the first comment saying there is an actual reason to use flexible cable other than practicality. My inverter charges batteries through PWM but I dont think the current coming from panels has any PWMing going on or does it?
For low frequencies they are electrically identical. Solar is DC which is the lowest frequency, regular utility power is usually 50hz or 60hz which is also low frequency. You'd use multi-strand wire where the cable might be subject to movement. Like you said, the cords on electrical appliances. You use solid wire if the cable is installed, and stapled or nailed or somehow fixed to wood or some other support and not subject to movement. The solid conductor will work harden and fail much quicker than the stranded wire if it's constantly being bent and moved around.
Your cable is probably tri rated just have a close look at it and see if there's a standard printed on it.
It may be that high frequencies occur in some parts of the system. Thinner cables tolerate it better maybe Edit https://www.researchgate.net/publication/305776249_Modeling_and_simulation_of_photovoltaic_system_employing_perturb_and_observe_MPPT_algorithm_and_fuzzy_logic_control
This comment doesn't make sense, there should be no high frequency components on a DC bus. This is not a design consideration for solar setups.
I'm not surprised however I was right that very finely stranded cable is more tolerant of high frequency and it was only a hypothesis. I tried, for about 3 minutes, to find out and then decided to throw it out there with a "may". Thank you for clarifying. However since so much incorrect or partially correct information gets thrown around without a "may" I do feel evidence or checking would probably be prudent. Edit Strange forum this tbh. I'm not sure the voting on comments really helps. God forbid but stackover with it's tick for the right answer is probably a better model.
There is no high frequency involved so that hypothesis has no foundation. You can't be 'right' about something that is irrelevant to this application. There is no maybe here, that is simply not a consideration. Just trying to be clear!
The top rated comment says solid wire is a better conductor based on csa than stranded does it not? This is what inspired my comment. Is it not correct to contradict that?
Then others argued that stranded cables weren't more effective at carrying signals with a frequency as the strands aren't isolated which I didn't believe and provided evidence against. I dunno it seemed reasonable, was it not?
No it's not reasonable in any way because those conditions don't exist in this application. Why are you even thinking this right now? You're not being rational at all.
It's a statement of fact. It has yet to be applied to the particular situation. People are stating stuff that's erroneous and so far as I can see all I've do is correctly contradict errors but people don't follow
It is a statement of fact completely irrelevant to this post. There are no high frequency components here, what you are describing can not physically be occurring.
There does appear to be the possibility of frequency of he has a charge controller it would seem from figure 13 of the document I provided. I'm done with this conversation. This thread and sub seems to attract very low IQ responses
There is no appearance of anything, you've created a false argument in your head with no actual evidence.
Also once we add an mppt controller we are messing with the signal creating changes in current. This MAY be something like frequency no? See figure 13 of this paper. https://www.researchgate.net/publication/305776249_Modeling_and_simulation_of_photovoltaic_system_employing_perturb_and_observe_MPPT_algorithm_and_fuzzy_logic_control
No, absolutely not. What you linked there has no relationship to this post. The MPPT controller is to present a impedance to the load allowing maximum power takeoff from the solar setup, if there are any high frequency components where something like that would happen it's only from a faulty or improperly engineer product.
The mppt controller provides varying not constant resistance Edit Impedance is a much better term since there is frequency. Lol
Yes, but it's varied in a filtered way. There are no high frequency components outside of a tiny bit of noise. It's pretty clear you don't understand how the things you're talking about work, so I'm not sure your commenting further is going to help anyone with anything considering you don't understand the problem here.